Plotter



` (No Model.) F. O; STOWELL.

PLOTTBR.

W No. 509,885. Ptentea Nov. 211 1898.

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//, Ilu/enia?? draftsmens circular UNiTED I TATES FRANK o. srowELL, or soMERVILLE, MAssAol-IUsETTs PLofTTER.

SPECIFICATION forming part of Letters Patent No. 509,335, dated November 21 1893.

Ap'plicstttion filed January 16, 1893i Serial No. 458,466-- (No model.)

To a/ZZ whom, it may concern:

e it known that I, FRANK O. STOWELL, av cltlen of the UnitedStates, residing at Somerv1lle,in the county of Middles'ez` and State of ,Massachusetts have invented a newand useful Drawing-Templet, of which the followmg 1s a specification.

My invention relates to improve'ments'in templets (sometimes called railroad curves), the object of said improvement being a templet which, though made of thinner material than common, is still less liable to blot When used with a drawing or ruling pen than the templets in present use. Iattain this object by the device illustrated in the accompanying drawings, in whichi Figure 1 is a plan view (full size) of a No. 8 templet '12. e. a templet the radius of each curved edge of which is eight inches. Fig. 2 is a cross section (considerably enlarged) of a templet showing construction of the ruling edges. Fig. 3 is'a cross section at the tangent points a b (Fig. 1.) enlarged three times for purposes of greater clearness.

The templets in present use are made principally of hard rubber or Wood, the stock from which they are cut varying from three thirtyseconds to three-sixteenths of an inch in thickness. This thickness is necessaryfor two reasons: first, strength; second, to avoid the danger of blotting when using a ruling pen filled with ink. On the other hand, since a complete set numbers from seventy-five to one hundred templets, this thickness becomes a'great objection on the score of excessive bulk. i

vIn contrast with present uses, I shall make my templets of metal, preferably of a compound of zinc and aluminum, though any suitable material having sufficie'nt strength may be used. By using metal I shall be enabled to make a templet less than one-sixteenth of aninch in thickness, which will be Stronger than the much more bulky curves made of Wood or rubber or paper.` A templet vof the thiokne'ss I design if made on the lines of those in present use, would be useless owing tovthe certainty of blotting when using a ruling pen. To avoid this danger of blotting with a thin templet is the object of my invention and I accomplish it by finishing my templets with specially beveled edges, instead of the vVertical edges common in templets in present use.

I have designed two forms of beveled edges for each templet. These edges are best shown in Fig. 2 in which the thickness of the templet has been greatly magnified for the sake of clearer illustration. One edge of the templet is first cut on a suitable bevel of about forty-five .degrees as indicated by the solid and dotted line c d. The sharp knife edge shown by the dotted lines at d is then trimmed ofl' to a slightly-blunter ro'und edge indicated by the solid portion-of the circle e.` The finished edge of the curve is represented by the solid or full lines, the whole circle e being drawn simply to 'show by comparison the circular nature of the rounded edge of the templet. The other edge of the templet is cut with a double bevel or diamondv shaped edge shown, Fig. 2, by full and dotted linest' g and g h 70. As before the' sharp knife edge forined at g is cut away leaving the blunt round edge shown by solid part of circle j. As before the finished edge is represented by the solid or full lines, the complete circle being drawn simply to show the relation of the finished edge of the templet. to a circle.

.Respecting the object of two forms of ruling edge on each templet it is intended that in using the templets with a soft pencil hfor example, the blunt edge j will be used, as the sharper edge at e would cut into wood or lead. Again, specially fine line work should be done with edge j, as the pen guiding edge is nearer the paper thanguiding surface e of 'the other edge of the templet. Lowering the guiding edge for fine line work will not be likely to cause blotting, as'in such work it is not desirable to have the ruling pen very full of ink. The guiding edge eis raised as high from the surface of the paper as the thickness of the templet will'admit and it is intended for all ordinary work with ruling pen and for complete' Safety in drawing heavy lines with pen heavily charged with ink.

The straight edges aV o and on Fig. 1 Vare respectively tangent to'the curved edges avl and b m at the points a and b. These edges enable the draftsman to once place the ICQ tempie-t so that its Curved edge Will be tangent to a straight line at any point on the iatter that he may elect.

Fig. 8 is a cross section (enlarged three times) of tempiet Fig. 1 at the tangent points ab. It shows manner of using ruiing pen and pencil on different edges of the templet as advised above. Itis indifferent as to how the two forms of beveled edges are distributed between the convex and concave edges ot' the templet, as I finish both edges ot' a given templet with the same radius.

I' am aware that circular templets terminating in a short piece of tangent at One end have been made before. such broadly; but

Therefore I do not claim WhatI do claim as my invention, anddesire to secure by Letters Patent, is-

A metailic circnlar templet in which both the concave and conveX edges a Z and b 'm have equai radii and terminate in short pieces a 0 and b n of tangent respectively, at one end of each cui'ved edge; also in which one edge ot'said tempiet is cut on a single bevel c d of about torty-five degrees, the other edge on a double or diamond shaped bevel fg h, the acute or knife edges d and g of said bevels being rounded ofit 01' ti'uncated by circnlai' surfaces e and 'i h substantialiy in the manner-described and for the purpose set forth.

FRANK O. STOWELL.

Witnesses:

G. B. STOWELL, JOSEPH J. GILES. 

